The present invention relates to a charge controller, obtained through photovoltaic solar panels, adapted for recharging a battery and preferably applied to automotive sector.
Normally the recharge of the batteries present in motor vehicles occurs through one or more alternators, which generate a very high power.
Said power is used for the recharge of the batteries.
Such alternators are electric devices which intrinsically are sources of electromagnetic noise.
Such noise generated by the alternator must be so limited in order to avoid damaging the electronic devices comprised inside the motor vehicle.
In the automotive field, the devices and electronic circuits present in the motor vehicle, must fulfill numerous Standards regarding electromagnetic compatibility.
Every circuit and electronic device is in fact an involuntary source of electromagnetic noise which, through the connection lines among the various devices, spread in the various circuits and neighboring devices.
The electronic devices, when subject to electromagnetic conducted or radiated noise, can modify their behavior so causing problems to the circuit in which they are operating.
Such problems can be different as for example when wrong data are received or one or more devices are damaged when not the entire circuit.
Systems of solar panels are further known, which through the tracker of the point of maximum power, known with the abbreviation MPPT, reach the maximum of the performances of the solar panel, by varying the working point on the voltage/current function of the photovoltaic solar panel, in function of the level of solar radiation.
Usually solar panels are placed on the top of buildings and in solar fields.
In such applications the power with which the panels are irradiated, varies slowly during the day.
Usually the solar panels are used for generating electric energy which, when suitably converted, is input into the grid as an alternate current (50 Hz or 60 Hz).
The control circuit in such applications comprises an MPPT which must follow the even slow variations of the irradiation of the panel, so that the maximum transfer of power is guaranteed; downstream of it the inverter device converts such energy from continuous current to alternate current inputting it thereafter in the electricity supply.
Said inverters further play a protective role for the system upwards, and in particular for the MPPT device, from the noise in the electricity network.
Solar panels applied on vehicles are further known, as for example automobiles defined as hybrid in which in addition to the internal combustion engine an electric motor is present which, by cooperating with the internal combustion engine, reduces the fuel consumption of the vehicle.
The electric motor of such hybrid cars is supplied by solar panels and batteries.
Said batteries usually cumulate the energy produced by the panels when the energy produced by the panels is not instantaneously exploited neither by the electric engine, nor by other electronic devices present on the vehicle.
Patent application US2010084208A1 actually describes such application but it does not give a technical solution to the control of the energy produced by the solar panels, to the achievement of the maximum power from such panels when boundary conditions vary, nor it indicates devices for the control and preservation of the system itself from the noise.
The batteries are very sensitive devices which rapidly and very easily lose their technical features so reducing their useful life.
Furthermore the voltage at the ends of the battery varies as a function of at least: the temperature, the external temperature and the level of charge of the battery itself.
It is known that an overcharge and/or over-discharge of the battery penalizes the future performances of the battery itself by consequently reducing the useful life of such device.
Normally the solar panel is adapted in power, in order to transfer the maximum power to the circuits downwards, so totally exploiting the normally limited power produced by the panel itself.
So it is very complicated to interface a solar panel with a battery, as the voltage at the ends of the two devices varies even with the variation of the temperature but following different functions.
Furthermore it is difficult to preserve the overall system, in addition to the solar panel and the battery, from possible damages which can compromise the useful life of the devices.
A further problem of the application of solar panels to the automotive field relates to the safety of the device as the MPPT device which, in this kind of applications, is more subject to noise which can cause its malfunction if not its breaking.
In particular, in the automotive field the battery is subject to particular electric impulses, as for example the impulse generated when a power source device is left in open circuit condition for more than a determined period of time and to which a charge is subsequently connected.
Such impulse is known as Load-dump and has a limited duration as defined by the automotive Standard ISO7637.
Said problem arises from the lack of a protection device from the noise which, in its classical applications was made by the inverter.
Patent WO2010/083460A1 describes a control system of the charge produced by a solar panel for managing various devices comprised in a motor vehicle as air conditioning, lights fans etc., without describing in detail neither the control nor the protection circuits of the system itself from possible electromagnetic noise which can damage the system itself.
U.S. Pat. No. 6,204,645B1 describes a control circuit of the charge produced by solar panels for storing and/or instantaneously using such charge, which does not provide for the use of a MPPT for always obtaining the maximum power transfer.
SUMMARY OF THE INVENTION